What is HDR?

Keeping track of the latest audio and video tech can be daunting. Thankfully, High-Def Digest has you covered. Welcome to our new Home Theater 101 series, where we'll be explaining emerging technologies while also recommending the very best possible A/V gadgets n' gear you can buy at your particular budget level.

And when it comes to recent display advancements, few are as buzzworthy as HIGH DYNAMIC RANGE.

But just what exactly is HDR and how does it work? And what's the deal with all of the competing formats? Fret not! If you don't know the difference between HDR10 and Dolby Vision, this guide is here to breakdown the ins and outs of High Dynamic Range. So, without further ado, let's dive right into...

HOME THEATER 101WHAT IS HDR?

THE BASICS

High Dynamic Range, or HDR for short, is an advanced display and image mastering technology used on select 4K TVs and Ultra HD content. The process uses expanded brightness to improve contrast between dark and light aspects of an image, bringing out deeper black levels and more realistic details in specular highlights -- like the sun reflecting off of an ocean -- in specially graded HDR material.

This increased brightness performance is measured in nits. In general terms, the more nits a display can produce, the brighter the image and greater the HDR performance will be. The UHD Alliance currently requires LCD displays to produce more than 1000 nits peak brightness and less than 0.05 nits black level, or OLED displays to produce more than 540 nits peak brightness and less than 0.0005 nits black level to receive Ultra HD Premium Certification, ensuring an optimal HDR experience. With that said, there are still many displays that offer some level of HDR performance without reaching those numbers.

In addition to enhanced contrast, HDR is often also bundled with support for a Wide Color Gamut (WCG), offering a greater range of colors than those found in traditional HD sources and TVs using the previous Rec. 709 standard. This means that WCG content and displays can now produce more realistic colors, providing a more true-to-life representation of an image. Though current Ultra HD and HDR specs provide support for the Rec. 2020 wide color gamut, wider color gamut content available now is typically produced in the DCI-P3 color space (aka the color space where commercial cinemas operate).

Check out the chart below to see the differences between each gamut. The entire curve represents the full visible color spectrum. The smallest triangle represents the old Rec. 709 gamut; the solid triangle represents the wider DCI-P3 gamut; and the large dotted triangle represents the Rec. 2020 gamut. (Source: AVS Forum)

As you can see, the Rec. 709 gamut is missing out on many of the colors covered by the larger DCI-P3 and Rec. 2020 color spaces, allowing the wider gamuts to produce hues that don't even exist in the previous standard.

When content is graded in HDR with WCG, the video is usually encoded with metadata. This metadata is then interpreted by an HDR display during playback, telling the TV what colors to render and how bright the HDR highlights should appear. HDR metadata is typically implemented in one of two ways: static or dynamic.

Static metadata uses the same HDR-grading for the entire video, offering one expanded range for the full runtime. In practice, this type of metadata leads to some dim scenes looking darker than they were originally intended. Meanwhile, dynamic metadata is able to adjust brightness levels on a scene-by-scene or even frame-by-frame basis, offering a more accurate HDR experience.

There are currently several different competing and co-existing HDR formats, with the three main options being: HDR10, HDR10+, and Dolby Vision, offering a variety of specific performance quirks, advantages, and disadvantages.

HDR10 & HDR10+

The default HDR standard for most content, including Ultra HD Blu-ray discs, is HDR10, an open standard High Dynamic Range content and playback solution. The base HDR10 format uses static metadata while a new expanded version of the tech, called HDR10+, uses dynamic metadata. HDR10 and HDR10+ both support the Rec. 2020 color space, a bit depth of 10-bits, and mastering for up to 4,000 nits peak brightness with a typical target output of 1,000 nits.

HDR10 playback is supported through the widest variety of displays on the market from manufacturers like Sony, Samsung, LG, VIZIO, TCL, and Hisense. HDR10 is also the required base HDR format for 4K Ultra HD Blu-ray discs. Likewise, HDR10 content is available through several streaming services like Netflix, VUDU, iTunes, and Amazon Prime Video, offering a growing collection of titles.

In order to watch HDR10 content, users will need an HDR10 capable display with internal support for HDR10 streaming apps and/or an external Ultra HD Blu-ray player or HDR capable set-top box. The format requires an HDMI 2.0a connection for external sources and HDCP 2.2 compliance for copyrighted material. Likewise, AV receivers need to meet those same specs in order to pass-through HDR10 video from connected players.

Meanwhile, the dynamic HDR10+ format is currently supported by all of Samsung's 2017 and 2018 HDR TVs. As of press time, the only source for HDR10+ content is Amazon Prime Video, though HDR10+ titles are expected to be released from 20th Century Fox and Warner Bros. later this year. Ultra HD Blu-ray players with HDR10+ support are also in the works from Samsung and Panasonic.

Though HDR10+ dynamic metadata should only technically be possible over the new HDMI 2.1 spec, HDR10+ is expected to be able to work over the current HDMI 2.0 spec thanks to a process called "Infoframe," allowing for the addition of 24KB of metadata. Samsung already has the process working, but the method is still being finalized and is pending approval from the company's partners. On that note, it remains unclear if current HDMI 2.0 AV Receivers will need a specific HDR10+ firmware update to be able to pass-through the format.

DOLBY VISION

Serving as the main competitor to HDR10 and HDR10+, Dolby Vision is a proprietary end-to-end HDR format that covers content creation and playback. Versions of the format are available in cinemas and home theaters, with the theatrical implementation being an integral part of the Dolby Cinema process, which uses the Dolby Vision laser projection system. Currently, there are more than 100 Dolby Cinema locations around the globe (HERE is a list of Dolby Cinema at AMC locations here in the US).

Meanwhile, for the home theater, Dolby Vision supports the Rec. 2020 color space, a bit depth of 12-bits, and a current target peak output of 4,000 nits and a max output of 10,000 nits. Dolby Vision uses dynamic metadata and needs more specific hardware than HDR10, initially requiring displays to include a special Dolby Vision chipset (though recent developments have made software solutions a possibility).

Dolby Vision for the home theater is currently available on several displays from manufacturers like VIZIO, LG, TCL, and Sony. On the content side, Dolby Vision is an optional addition for HDR playback on 4K Ultra HD Blu-rays. Lionsgate, Warner Brothers, Paramount, Universal, Disney, Sony, and BBC have all released Ultra HD Blu-rays with Dolby Vision. In addition, Dolby Vision content is also available through streaming services like Netflix, Amazon Prime Video, iTunes, and VUDU.

ADDITIONAL HDR FORMATS

Outside of the main HDR10 and Dolby Vision standards there are few other emerging high dynamic range formats as well. Most notably, there is the Hybrid Log Gamma, or HLG, standard developed by the BBC and NHK. The royalty free HDR format is geared toward delivering high dynamic range content over live broadcasts. And unlike other formats, HLG's HDR process doesn't actually use any type of metadata. HLG support is now offered on many displays, including models from LG, Sony, Samsung, and VIZIO.

In addition, Technicolor's Advanced HDR solution is also geared toward broadcast high dynamic range, along with SDR to HDR conversion. According to Technicolor, Advanced HDR is actually "format agnostic and can take all HDR formats, as well as SDR formats, as inputs and then normalize and deliver all of them on any HDR or SDR device, ensuring a consistent experience in both HDR and SDR worlds." The tech is a combination of Technicolor HDR ITM which up-converts SDR to HDR, and Technicolor HDR which is able to distribute HDR and SDR content through one stream. So far, LG is the only manufacturer to make mention of Technicolor Advanced HDR support for its displays.

WHICH HDR FORMAT IS BEST?

Taking into account the industry's growing assortment of HDR methods, is there an easy pick for best format among the group? Well, not exactly, but based on what we've seen and know about the tech, dynamic metadata platforms definitely offer a notable edge over static metadata ones. There isn't enough content on the market just yet to fairly compare HDR10+ and Dolby Vision in order to declare a definitive winner, but both are generally capable of providing a superior HDR experience over standard HDR10.

RECOMMENDED GEAR

There are currently several great HDR display solutions on the market, covering a wide-range of price points and panel technologies. Here's a rundown of some recommended HDR gear available now...

TCL 6-Series 65R617 65-Inch 4K Ultra HD Roku TV ($1,000) - TCL's 6-Series just might the feature the best performance to price ratio of any new display for 2018. The 4K TV features Dolby Vision and HDR10 support, along with the Roku OS smart TV platform. In addition, the set uses full array local dimming with 120 zones (96 on the 55-inch model) for improved black levels and contrast. Likewise, the panel incorporates NBP Photon technology with LED phosphors to provide Wide Color Gamut support. A 55-inch model is available as well for an introductory price of just $650.

LG OLED65C8PUA 65" 4K Ultra HD OLED TV ($3,198) - As one of LG's top-of-the-line 2018 OLED TVs, this display offers some of the best overall picture quality on the market, including perfect blacks and the company's new α (Alpha) 9 intelligent processor for improved image and color performance over last year's models. In addition, the panel also supports onboard Dolby Atmos audio and LG's 4K Cinema HDR suite of high dynamic range formats with wide color gamut capabilities, including Advanced HDR by Technicolor, Dolby Vision, HDR10, and HLG (Hybrid Log-Gamma). Meanwhile, the TV's new ThinQ AI tech allows customers to take advantage of advanced voice assistant features by speaking directly into the remote, enabling users to search for information, images or videos through verbal requests. 55-inch($2,297) and 77-inch ($8,997) C8 models are available as well.

Samsung QN65Q9F 65" QLED 4K Ultra HD ($3,498, full review coming soon!) - As Samsung's top-of-line 2018 LCD display, the new Q9 QLED offers some of the industry's leading color volume and HDR brightness specs. And though blacks still aren't quite as impressive as an OLED panel, the company's return to full array local dimming results in fantastic contrast and a huge improvement over the 2017 Q9's edge-lit dimming. Quantum dot technology for wide color gamut coverage is featured as well, along with support for HDR10, HLG, and the new dynamic HDR10+ format. Smart TV functions with Bixby Voice control and a new Ambient Mode round out the premium package. A 75-inch ($5,998) model is also available.

Check out the chart below to see the differences between each gamut. The entire curve represents the full visible color spectrum. The smallest triangle represents the old Rec. 709 gamut; the solid triangle represents the wider DCI-P3 gamut; and the large dotted triangle represents the Rec. 2020 gamut. (Source: AVS Forum)

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Founded in April 2006, High-Def Digest is the ultimate guide for High-Def enthusiasts who demand only the best that money can buy. Updated daily and in real-time, we track all high-def disc news and release dates, and review the latest disc titles.